Patent GB-563928-A (GB)
Title: Improvements in regulation of steam boilers
IPC: F22D3/00
Filed: 1941-09-23
Abstract: 563,928. Automatic control systems for steam generators. LOUMIET, J. P. Sept. 23, 1941, No. 2324. Convention date, Oct. 17; 1940. [Class 38 (iv)] [Also in Groups. XIX, XXIX and XXXVIII] Fluid level; fluid pressure.-Apparatus for maintaining steam pressure or water level in a boiler at a normal value comprises means for effecting electrically continuous regulation in a restoring direction while the value is departing from normal, for arresting the regulation in that direction after departure has ceased andthe value has begun to approach normal, and for maintaining the arrest while approach continues. The arrest may be delayed somewhat. Means may also be provided to effect a regulation in the opposite sense during the approach to normal to compensate an over correction during departure. Correction may be obtained by the control of a feed valve or feed pump controlling water supply or an element of combustion and operated by a reversible electric motor. A column of mercury enclosed in a horizontal capillary tube treated between vertical columns of fluid of low conductivity may make contact between alternative pairs of contacts according to water level conditions to effect control, or if a steel tube be used to contain the mercury the variations in the combined resistance of the steel and mercury - may be utilized. The latter principle is also used in a vertical tube for steam pressure control. Figs. 1 and 2 show a horizontal capillary tube E between U-tubes A-B, G-H, of which the upper parts of B and G contain oil and H contains a dense liquid, such as salt water ; a tube J and the tube A, which are connected respectively to water and steam spaces in the boiler Ch, contain water. The mercury column co-operates with contact pairs a ... d which control the current supply to relays am, bm controlling a reversible A.C. motor M and the auxiliary relays C, D and the arrangement of contacts and circuits is such as to obtain a control as set forth above. Fig. 5 shows a system of water level control wherein terminals a<SP>3</SP>, b<SP>3</SP> in a steel tube containing a horizontal mercury column are connected through an ammeter A', the needle of which indicates water level by its position and travels over resistances C<SP>17</SP>, C<SP>27</SP> on opposite sides of a position denoting a desired water level to energize selectively and variably solenoids B, B<SP>1</SP> operating oppositely upon a normally centralized member K<SP>17</SP> carrying insulated contact members F', F<SP>17</SP> adapted respectively to bridge contact pairs f<SP>7</SP> J<SP>7</SP> and f<SP>17</SP>, J<SP>17</SP>. The elements J', J<SP>17</SP> are pins mechanically coupled together and displaced by the member K<SP>17</SP> so that contact is broken immediately movement of this member reverses. The contact pairs control relays E<SP>7</SP>, E<SP>17</SP> for reversibly controlling the A.C. motor M which may control a steam engine or electric motor driving a feed pump. A modification of this arrangement is described for the control of steam pressure in which a member such as K<SP>17</SP> directly controls switches in the reversing circuits of the motor contacts of these switches being displaced to prevent circuit closure by solenoids controlled by a lost-motion switch driven from the motor, as well as by cam devices on the control member. In a further modification, the variable current through the mercury and steel tube passes through a solenoid B<SP>8</SP>, Fig. 6, to cause displacement of a magnetic member A<SP>18</SP> in reference to a fixed member A<SP>8</SP> and so control the reversing switch for the motor. Specifications 541,840, 544,130 and 552,364 are referred to. The Specification as open to inspection under Sect. 91 describes the operation of a control valve by a pinion and rack driven by a solenoid device similar to Fig. 6 and a lazy-tongs actuated by a solenoid of usual type. This subject-matter does not appear in the Specification as accepted.